Messages in this thread | | | Date | Tue, 10 Oct 2023 10:52:09 +0200 | Subject | Re: [PATCH v3] spmi: mtk-pmif: Serialize PMIF status check and command submission | From | AngeloGioacchino Del Regno <> |
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Il 19/09/23 22:12, Nícolas F. R. A. Prado ha scritto: > On Thu, Aug 10, 2023 at 06:03:53PM -0400, Nícolas F. R. A. Prado wrote: >> On Mon, Jul 24, 2023 at 11:47:33AM -0400, Nícolas F. R. A. Prado wrote: >>> Before writing the read or write command to the SPMI arbiter through the >>> PMIF interface, the current status of the channel is checked to ensure >>> it is idle. However, since the status only changes from idle when the >>> command is written, it is possible for two concurrent calls to determine >>> that the channel is idle and simultaneously send their commands. At this >>> point the PMIF interface hangs, with the status register no longer being >>> updated, and thus causing all subsequent operations to time out. >>> >>> This was observed on the mt8195-cherry-tomato-r2 machine, particularly >>> after commit 46600ab142f8 ("regulator: Set PROBE_PREFER_ASYNCHRONOUS for >>> drivers between 5.10 and 5.15") was applied, since then the two MT6315 >>> devices present on the SPMI bus would probe assynchronously and >>> sometimes (during probe or at a later point) read the bus >>> simultaneously, breaking the PMIF interface and consequently slowing >>> down the whole system. >>> >>> To fix the issue at its root cause, introduce locking around the channel >>> status check and the command write, so that both become an atomic >>> operation, preventing race conditions between two (or more) SPMI bus >>> read/write operations. A spinlock is used since this is a fast bus, as >>> indicated by the usage of the atomic variant of readl_poll, and >>> '.fast_io = true' being used in the mt6315 driver, so spinlocks are >>> already used for the regmap access. >>> >>> Fixes: b45b3ccef8c0 ("spmi: mediatek: Add support for MT6873/8192") >>> Signed-off-by: Nícolas F. R. A. Prado <nfraprado@collabora.com> >> >> Hi, >> >> gentle ping on this one. MT8195 Chromebooks sometimes boot to a broken state >> without it. > > Hi Stephen, > > once again kindling reminding you of this important fix for MediaTek platforms, > solving a real issue impacting basic functionality observed on the MT8195 > Chromebook. >
Hello Stephen,
can you please pick this one ASAP? MT8195 is broken without.
Thanks, Angelo
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